Recently, to reduce air pollution caused by exhaust gas of vehicles, the vehicles are being manufactured on the basis of research to ensure driving force by using an internal-combustion engine and/or an electric motor. Thus, the vehicles have evolved in the order of a hybrid vehicle, a plug-in hybrid vehicle, and an electric vehicle. In this case, the hybrid vehicle and the plug-in hybrid vehicle have an internal-combustion engine, an electric vehicle, and a battery pack, and the electric vehicle has an electric motor and a battery pack without an internal-combustion engine. In this case, the hybrid vehicle and the plug-in hybrid vehicle have an internal-combustion engine, an electric motor and a battery pack, and the electric vehicle has an electric motor and a battery pack without an internal-combustion engine.
In addition, the battery pack has also evolved with hybrid vehicles, plug-in hybrid vehicles, and electric vehicles. The battery pack is configured to be capable of being charged by power supplied from the outside of an electric vehicle or power produced in the electric vehicle. The battery pack has cooling ducts and a battery module between a lower case and an upper case. The cooling ducts introduce air from the outside to the inside of the battery pack so as to cool battery cells of the battery module using the air, and continuously discharge from the inside toward the outside of the battery pack.
Here, the cooling ducts are partially exposed to the outside air from an outer wall of the battery pack to suck air from the outside of the battery pack. Also, the upper case is curved according to shapes of the cooling ducts and closely attached to the lower case and the cooling ducts using a sealing member. However, if the cooling duct and the upper case are not matched, the cooling duct and the upper case have an unnecessary space between the cooling duct and the sealing member or between the sealing member and the upper case. The unnecessary space partially discharges the air to be introduced into the battery module via the cooling duct, thereby degrading the cooling performance of the cooling duct.
Accordingly, a shape of the cooling duct installed between the lower case and the upper case greatly affects cooling effects of battery cells per unit time. Many studies have been conducted on the shape of the cooling duct. One example of the studies has been disclosed in Korean Patent Laid-Open Publication No. 10-2012-0122000 (published on Nov. 7, 2012), entitled ‘Battery Pack with Inlet and Outlet Optimization Structure’. The battery pack has a cell module, an inlet duct, and an outlet duct in an outer case, and has an inlet cover and an outlet cover on an upper side of the outer case.
The inlet duct communicates with the inlet cover, and the outlet duct communicates with the outlet cover. Here, the inlet cover and the outlet cover are respectively located on different sides of the outer case. However, in the case of the battery pack, the outside air sequentially passes through the inlet cover, the inlet duct, the battery cells of the cell module, the outlet duct, and the outlet cover, so that battery cells located near the outlet cover may accumulate heat under the influence of hot air that has exchanged heat with other battery cells. The heat accumulation of some of the battery cells deteriorates electrical characteristics of the battery module.